66th Honinbo

The 66th Honinbo began league play on 7 October 2010 and completed on July 21, 2011. Title holder Yamashita Keigo retained his title over challenger Hane Naoki by a score of 4-3. Yamashita Keigo won the first three games, Hane Naoki the next three, and Yamashita Keigo the final game.

Preliminary tournament

The preliminary tournament started on 8 April 2010. Hane Naoki, Iyama Yuta, Takao Shinji, and Cho U retained their place in the Honinbo league from the 65th Honinbo. These players were joined by the winners of the preliminary tournament: Cho Sonjin, Seto Taiki, O Rissei, and Kobayashi Satoru.

	Quarter-finals				Semi-finals				Final
	13 May
	Yamashiro Hiroshi	1
					17 June
	Fujita Akihiko	0
					Yamashiro Hiroshi	1
	27 May
					Takashima Takeshi	0
	Goto Shungo	0
									12 August
	Takashima Takeshi	1
									Yamashiro Hiroshi	0
	20 May
									Cho Sonjin	1
	Ohashi Hirofumi	0
					1 July
	Uchida Shuhei	1
					Uchida Shuhei	0
	27 May
					Cho Sonjin	1
	Cho Sonjin	1
	Yamada Kimio	0

	Quarter-finals				Semi-finals				Final
	13 May
	Hoshino Masaki	0
					10 June
	Kataoka Satoshi	1
					Kataoka Satoshi	1
	13 May
					Obuchi Morito	0
	Obuchi Morito	1
									29 July
	Yasuda Yasutoshi	0
									Kataoka Satoshi	0
	13 May
									Seto Taiki	1
	Yamada Noriyoshi	0
					24 June
	Akiyama Jiro	1
					Akiyama Jiro	0
	27 May
					Seto Taiki	1
	Seto Taiki	1
	Mimura Tomoyasu	0

	Quarter-finals				Semi-finals				Final
	13 May
	Nakane Naoyuki	0
					24 June
	Nakano Hironari	1
					Nakano Hironari	0
	3 June
					Kono Rin	1
	Ogata Masaki	0
									2 September
	Kono Rin	1
									Kono Rin	0
	20 May
									O Rissei	1
	O Rissei	1
					15 July
	Mochizuki Kenichi	0
					O Rissei	1
	27 May
					Yuki Satoshi	0
	Kamimura Haruo	0
	Yuki Satoshi	1

	Quarter-finals				Semi-finals				Final
	22 April
	O Meien	0
					10 June
	Kobayashi Satoru	1
					Kobayashi Satoru	1
	13 May
					Ishida Atsushi	0
	Shida Tatsuya	0
									19 August
	Ishida Atsushi	1
									Kobayashi Satoru	1
	3 June
									Suzuki Shinji	0
	Mizokami Tomochika	0
					24 June
	Suzuki Shinji	1
					Suzuki Shinji	1
	13 May
					Cho Chikun	0
	Cho Chikun	1
	Takemiya Masaki	0

League play

League play commenced on 7 October after the preliminaries, which finished on 2 September. Hane Naoki, who lost the Honinbo title to Yamashita Keigo the year prior, won the right to challenge Keigo for the title.

Player	H.N.	I.Y.	T.S.	C.U.	O.R.	K.S.	C.S.	S.T.	Record	Notes
Hane Naoki	–	B+R	W+R	X	W+0.5	B+R	W+R	B+R	6–1	Challenger
Iyama Yuta	X	–	B+R	X	X	W+R	B+R	W+R	4–3
Takao Shinji	X	X	–	B+1.5	X	X	W+R	X	2–5	Eliminated
Cho U	W+R	B+0.5	X	–	B+3.5	X	B+R	X	4–3
O Rissei	X	W+R	B+R	X	–	X	X	B+R	3–4	Eliminated
Kobayashi Satoru	X	X	W+2.5	B+4.5	W+R	–	X	X	3–4	Eliminated
Cho Sonjin	X	X	X	X	B+R	W+11.5	–	X	2–5	Eliminated
Seto Taiki	X	X	W+R	B+R	X	B+3.5	W+R	–	4–3

Finals

Player	1	2	3	4	5	6	7	T
Yamashita Keigo (Honinbo)	W+7.5	B+R	W+1.5				W+4.5	4
Hane Naoki (Challenger)				W+0.5	B+R	W+7.5		3